Description of the Prior Art
In the known prior art of optical scanning of UPC (Universal Product Code) symbols, which are composed of alternating black and white bars to form a code, it is known that the nature of the optical scanning system which is utilized to read the code tended to discriminate against the white bars over the black bars. Accordingly, equalization circuits were utilized into the signal processing circuity to remedy this problem.
In a dissimilar art such as systems that read magnetic information on tape, it is well known that if the information cannot be properly read from the tape when the read circuits are at a nominal gain setting, the system will automatically switch to increase gain and a read cycle will again be tried. However, if too much noise is introduced into the read circuitry by the increased gain so that a read operation cannot be accomplished, then the gain is reduced to below nominal and a read cycle is again attempted. Hopefully, this third alternative permits a successful read to take place.
It is to be noted in the above magnetic read system that the different gains that are introduced are linear changes introduced into an amplifier as opposed to non-linear gains.